In the field of a military training program an infrared firing is usually exercised in which special targets are used that radiate a heat with a temperature higher than the temperature of the surrounding atmosphere for being recognizable also at night with any adequate nightsight view finder. In U.S. Ser. No. 792,978, Geuss, a target system for use in such infrared firing exercises is described as operating with targets that each comprise a wooden carrier material formed as a plate of uniform thickness which is covered on a front surface with a thin metallic layer of electrically conductive resistance material adapted for being heated by a heating current as supplied through a voltage step-down current step-up transformer.
When such a target system is being used it is highly desirable in having also the possibility of evaluating all of the shots that reach the target in the course of a firing exercise. Accordingly there are also in use already special hit sensors that comprise a piezoelectric element that forms a directly connected unit with an interference cable of such a length that when the piezoelectric element is fixed on the target its interconnection with a specific evaluation device for a corresponding remote control of the firing exercises may be secured. There are presently known different kinds of such evaluation devices which for a connection with such hit sensors necessitate the use of a connector cable with either two or with seven pins on a cable plug member which are to be inserted into a corresponding number of pin holes of two correspondingly different kinds of sensing inputs of such devices.
With such an arrangement in mind it becomes obvious that such hit sensors are quite often destroyed by straying shots that either reach the piezoelectric element or much more frequently its connector cable. It is therefore necessary to store at the exercise site a rather large number of such hit sensors of both kinds for allowing an immediate exchange whenever such a hit sensor has been destroyed during the course of a firing exercise. Since particularly the piezoelectric element forms a rather expensive part of such hit sensors such a frequent exchange is of course very costly also under the viewpoint that even with a damage only of the connector cable it no longer is possible to repeatedly use the piezoelectric element.
This invention deals with the object of providing a hit sensor which with the use of any suitably designed retainer means will allow a repeated use of the piezoelectric element as long as the same has not been directly damaged during the course of a firing exercise.
This object of the present invention is accomplished by a retainer means which includes a clamping device adapted for being fixed to a target and having a recess in which a piezoelectric element for sensing each shot at the target is arranged as embedded in a molded insulating material such as preferably a thermosetting material. The piezoelectric element is connected by means of a resistor that is arranged outside of the recess to a connector cable which may be of either of the two kinds with accordingly either two or seven pins on a cable plug member so that with the provision of cables having at their end opposite to this cable plug member a plug adaptor member that incorporates the resistor with a cable specific resistivity it then will be possible to connect the different kinds of cables without any problems with the piezoelectric element when the same according to a specific feature of the invention is provided with fixedly interconnected connector pins for its connection with the plug adaptor member of the connector cables.